The invention relates to a device for sealing the contact zone between two apparatus parts, which are movable relative to one another, this device comprising a sealing element which extends along the contact zone and is fixed on the first apparatus part and also a mating surface which is provided on the second apparatus part and comes into contact with the sealing element in a closed position of the two apparatus parts.
Devices of this type are provided for example in shut-off elements such as pivoting flaps, rotating flaps or slide plates which are provided in hot gas pipelines of large dimensions where they ensure a reliable gas-tight seal in the closed position. The sealing element which is used in this case must have a sufficiently great resilient travel in order to be able to compensate for irregularities on the mating surface and expansions of the material due to the hot gas.
Therefore the most varied cross-sectional shapes for the sealing element are known in the art. The sealing element is usually formed by an elongated spring steel strip which has two planar longitudinal edge regions as well as a zone which is disposed between these two planar longitudinal edge regions and is curved in the shape of an arc at right angles to the longitudinal direction of the spring steel strip, the sealing element resting resiliently on the mating surface with a part of this curved zone in the closed position of both apparatus parts. In a known construction of this type, the two planar longitudinal edge regions of the sealing element constitute a straight-line extension of the zone which is curved in the shape of an arc, the two planar longitudinal edge regions being clamped in a separate clamping arrangement. However, with this construction the considerable height of the construction and difficult installation are particularly disadvantageous.
A sealing element is known from EP-A-0 340 430 which has at least one chamfer between a longitudinal edge region and the curved zone and is otherwise shaped so that the two longitudinal edge regions lying one above the other point towards the same side and are clamped together by means of a clamping arrangement. The height of the construction can be markedly reduced by the chamfering of one or both longitudinal edge regions.
A suitable sealing element, particularly for hot gas pipelines, must not only have sufficient resiliency but must also have a sufficiently great resilient travel in order to compensate for the thermal expansions which are to be expected, but, moreover, it must also have sufficient rigidity. So long as the sealing element is not resting on the mating surface, it is in fact exposed to an extraordinarily strong flow of hot gas. The flow speed increases substantially, above all during the closing operation, so that self-oscillations of the sealing element can occur. In the long term, such self-oscillations can lead to damage or fracture of the sealing element. In practice, it has been shown that chamfered sealing elements are particularly at risk in this connection.
A sealing element is known from DE-C-198 28 896 which is formed by a strip of spring steel sheet which extends along the contact zone, is curved in the shape of a hollow section and of which the two Longitudinal edge regions form gripping edges which are clamped on one of the two apparatus parts at a distance from one another which amounts to at least 10% of the width of the sealing element, wherein in the closed position of the shut-off element the sealing element rests by spring action with a sealing force on the seal seat with a sealing zone which has a convex curvature relative to the seal seat. The sealing zone of this strip of spring steel sheet is bent by plastic deformation in the form of a roof ridge with roof surfaces adjoining it on both sides, the two roof surfaces being oriented at an angle of 60xc2x0 to 160xc2x0 relative to one another. A further bend which is produced by plastic deformation and is convex towards the exterior is provided in each case on the longitudinal edge of the two roof surfaces remote from the roof ridge, and a side surface which is planar at least in a first portion and has the gripping edge formed on its free longitudinal edge in each case adjoins the said bend. Such a sealing element facilitates substantially greater resilient travel than hitherto, particularly resilient travel of up to 30 mm, without the rigidity of the sealing element being unacceptably decreased. Nevertheless, even with this element, self-oscillations due to the high gas speeds cannot be avoided, particularly during the closing operation. Thus with this sealing element too the chamfered regions are endangered to a considerable extent due to the self-oscillations.
In certain cases in which a hundred percent sealing is necessary, two sealing elements are disposed adjacent to one another and confining air is blown into the space between them. In order to ensure reliable sealing, the confining air must be blown in with a higher pressure than the hot gas stream. However, the sealing device according to DE-C-198 28 896 is less suitable for this, since the relatively large roof surfaces buckle inwards at relatively high pressure and can then lead to the sealing element becoming detached from the mating surface.
The object of the invention therefore is to provide a device for sealing the contact zone between two apparatus parts which are movable relative to one another which is distinguished by good sealing.
According to a first embodiment, the sealing element is formed by a resilient hollow body whichxe2x80x94in an open positionxe2x80x94has a circular cross-section at right angles to its longitudinal extent and rests resiliently on the mating surface with a part-zone in the closed position of the two apparatus parts.
The circular cross-section facilitates very great resilient travel in order in particular to be able to compensate for thermal expansions due to the effect of the temperature of any hot gases. Moreover, since the sealing element has no chamfers, it is distinguished by a long service life.
The hollow section body is preferably closed by a section made from spring steel which is closed in cross-section.
In an embodiment according to the invention at least one clamping strip is provided in the interior of the hollow section body, this clamping strip being fixed on the first apparatus part via openings in the hollow section body in order to grip the sealing element.
The sealing element according to a preferred embodiment also has means for stabilizing the hollow section body which are disposed in the hollow section body and fixed on the first apparatus part. In this way, self-oscillations of the sealing element in the open position can be avoided or reduced.
According to a further embodiment, the device for sealing the contact zone between two apparatus parts which are movable relative to one another comprises a sealing element which extends along the contact zone and is fixed on the first apparatus part and also a mating surface which is provided on the second apparatus part and comes into contact with the sealing element in a closed position of the two apparatus parts, the sealing element being formed by a resilient hollow section body which has at right angles to its longitudinal extent a part-zone which is curved in an arc shape in an open position of the two apparatus parts and rests resiliently on the mating surface in the closed position of the two apparatus parts. In the region of the contact zone with the sealing element, the mating surface has means for the delivery of confining air. In this way a hundred percent sealing of the contact zone between the two apparatus parts can be achieved.
Moreover, if the hollow section body has a circular cross-section at right angles to its longitudinal extentxe2x80x94in an open positionxe2x80x94a relatively wide contact zone between the two apparatus parts is produced in order to ensure sufficient space for installation of the means for delivery of the confining air.
The means for delivery of the confining air are advantageously formed by a slot which extends along the contact zone.